Hundreds of thousands of low-income adults will be eligible for health insurance starting April 1 under Michigan's expansion of Medicaid.

Gov. Rick Snyder told The Associated Press that he blessed the launch date after his administration tested computer systems and developed plans to get the word out to the public. Coverage will be retroactive to the first day of the month in which people apply.

Snyder, who fought to persuade fellow Republicans in the Legislature to agree to the Medicaid expansion under the contentious federal health care law, said he expects 320,000 residents to sign up in the first 12 months. The number could grow as high as 470,000 over time, he said.

"It's a great program and hopefully something that will create a better quality of life ... and help save society money over the long term," the governor said in a Wednesday phone interview.

Early April had long been the target date for starting the "Healthy Michigan" program, but Snyder wanted to be cautious after the federal government's botched rollout of healthcare.gov, the insurance market for the middle class in 36 states including Michigan. His administration also was waiting for approval of a spending bill to account for a delay in the expansion, which Snyder had hoped to begin in January.

Medicaid already covers one in five Michigan residents, mainly low-income children, pregnant women, the disabled and some poorer working adults. Starting April 1, the expansion will cover adults making up to 133 percent of the poverty line — $15,500 for an individual, $26,500 for a family of three. Michigan now covers childless adults earning up to 35 percent of the poverty level.

The expansion establishes individual health savings accounts for adult recipients and requires them to pay up to 5 percent of their annual income toward the government health insurance program that Michigan runs through managed-care plans. Monthly premiums and copays can be reduced if participants engage in healthy behaviors — starting with completing a yearly health-risk assessment to identify smokers, substance abusers and those who are overweight or not up to date on vaccinations.

Snyder said he expects with more people being insured, there will be fewer visits to emergency rooms for expensive, uncompensated care, ultimately saving everyone money.

"People not having health care is a major challenge," Snyder said. "They're going to the emergency room for their care. Usually they're putting their care off for some time. It's an expense to us — uncompensated care has to be paid in some way."